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LRI Cathedral Port Muzzle Brake for ARC Mausingfield and Ruger RPR

LRI Cathedral Port Muzzle Brake for ARC Mausingfield and Ruger RPR

  • $ 17999

LRI has answered the need for a custom fitted muzzle brake for the both the Mausingfield from ARC and the The Ruger RPR.  The challenge with prefit barrels is knowing exactly where the barrel will index once assembled to the receiver.  A slight variation in tightening torque, type of thread lubricant used, quantity of thread lubricant, and normal variations in thread pitch diameter all play a critical role when "pulling up" a barrel to an action.  These variables make it impossible to know exactly where a barrel will index once installed.

Normally this is not a problem.  It doesn't reveal itself until we try to add accessories without the entire rifle being in our possession.  Lag time, shipping costs, and the risks associated with shipping firearms doesn't always make this a realistic option.

LRI's Solution:

By using a differential threading insert between the barrel and muzzle brake threads, you are now able to index the brake from home without any machine work or elaborate tools while preserving the clean fit and finish our installations are known for.  

This is the perfect solution for rifles using spanner type retention nuts and the RPR barrel nut system.

Here's how it works:

The muzzle is threaded for a conventional thread pitch like the popular 5/8-24 size so common on many barrels.  The brake itself has a 3/4-32 pitch female thread pitch.  The insert has both.  5/8 on the inside and 3/4 on its exterior.  The difference in pitch allows the insert to effectively alter the start position of the thread but because the shoulder is unaltered.  Only the clock position changes.  

All you have to is find the sweet spot by moving the insert in/out of the brake.  

(We advise clients to use a small amount of green or blue loctite on the threads during assembly.  Muzzles whip and vibrate heavily during shooting.  Loctite helps to ensure the brake will hold its position and stay tight.)

On a rifle such as the RPR this is powerful because there is simply no way to know where the barrel will time when fully assembled.  

Our variation solves the problem while still delivering the same level of performance as the original brake along with exceptional fit and finish.

The video is a time lapse of the process used here at LRI to fit every single Cathedral Port Brake we make.  Custom does not come in a box!



This brake is ONLY available to barrels fitted by LRI.  This brake is limited to barrel contours with a muzzle diameter of at least .820".

 As the video illustrates, the brake is contoured to match the barrel prior to porting.  This is the only way to deliver the fit and finish LRI is known for.  

When ordering your brake as an "add on" item, please ensure that you measure the diameter of your barrel at the shoulder of the muzzle threads using a micrometer or dial caliper in good working condition.  We will then machine the blank to fit.  

Note that most rifle barrels suffer from a certain degree of concentricity error between the bore and the outside contour.  As an "add on" item we have no way of ensuring that the brake will finish with a seamless appearing fit.  When doing this work in house during a barrel fitting job, we take the time to blend the two pieces as an assembly.  We have no way of doing this when we are machining the brake as an individual component.

We do not sell the brake or thread insert as a separate item.  Please make a note of this.  



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